This invention relates to an improved appliance for the chemical sterilization of small articles such as soft contact lenses, and more particularly relates to pressure relief venting of such appliances.
In recent years, extremely soft contact lenses have been fabricated from a pliable plastic material that has the advantage of being able to be worn for extended periods of time without causing discomfort. These plastics are quite hydrophilic, and for that reason these contact lenses are susceptible to contamination by microorganisms. Consequently, the user must sterilize or disinfect the lenses, generally on a daily basis.
Various disinfecting techniques are now used in which the lenses are heated in a closed vessel in the presence of a saline solution, the heat being of such intensity and duration as to destroy the contaminating microorganism. More recently, a sterilizing process has been utilized that does not require heating. This process utilizes a bactericide, for example hydrogen peroxide, which oxidizes the bacteria on the lenses. In accordance with this process, the lenses are immersed for several hours in a weak solution of hydrogen peroxide, generally a 3% solution. Also within the solution is a platinum catalyst which hastens the decomposition of the hydrogen peroxide. If a bactericide such as hydrogen peroxide is used, care must be taken to insure that the solution is sufficiently neutralized or broken down so that the possibility of discomfort or injury to the eye of the user is precluded. Accordingly, the lenses are kept in the bactericide solution for a sufficient length of time to destroy all of the bacteria, following which the lenses are introduced into a rinsing solution to rinse out excess bactericide which may have a concentration that is unacceptably high.
Another problem encountered in the foregoing process is that there is a buildup of gas pressure within the sterilizing chamber which may tend to cause leaking and/or spillage, especially when the cap of the unit is not sealed properly. In this regard, when the hydrogen peroxide is brought into contact with the platinum catalyst, the hydrogen peroxide solution tends to break down into water, with oxygen being liberated. The liberated oxygen will cause a pressure build-up within the vessel that must be vented to the atmosphere. In U.S. Pat. No. 4,011,941, there is shown and described a contact lens sterilizer using hydrogen peroxide and in which the oxygen pressure is relieved through the expansion of a rubber O-ring. Thus, the O-ring normally seals the unit, but also functions as a check valve. However, when the valve is "open", there is still the possibility of solution leaking therethrough. Moreover, an O-ring can lose its resiliency over a period of time causing improper or ineffective valve operation. Additionally, the O-ring can become displaced leaving an opening through which bacteria from the ambience may enter the sterilizing chamber.
In U.S. patent application Ser. No. 668,293, filed Nov. 5, 1984 (now allowed), which is incorporated herein by reference, an appliance is described for disinfecting contact lenses or the like which employs a hydrophobic membrane filter that continuously vents the buildup of gas within the unit during the disinfecting process, while at the same time keeping the unit effectively sealed against leakage of disinfecting solution and entrance of bacteria into the sterilizing chamber.